1. Field of the Invention
The present invention relates to a novel hydrazone compound and the use thereof in a nonlinear optical material and as an organic chelating agent.
2. Description of the Related Art
A nonlinear optical effect is applied to modulate the wavelength, phase and amplitude of a laser light in case of harmonics generation, optical switching, and optical mixing. The effect thus plays an important role in the field of information processing using light.
Hitherto, inorganic compound crystals have been mostly used as a nonlinear optical material exhibiting a nonlinear optical effect. However, their nonlinear optical effects are unsatisfactory. Recently, besides the inorganic compound crystals, various organic compounds have been found to possess a nonlinear optical constant considerably larger than those of inorganic compound crystals and to exhibit excellent resistance to optical damage.
General information on the organic nonlinear optical materials is disclosed in, for example, D. J. Williams et al., "Nonlinear Optical Properties of Organic and Polymeric Materials", American Chemical Society, 1983, and D.S. Chemla et al., "Nonlinear Optical Properties of Organic Molecules and Crystals", Academic Press Inc, 1987. The organic nonlinear optical material listed in these publications has a structural feature at a molecular level that an electron-donating functional group is allowed to bind to one end of a .pi. electron-system skeleton such as a benzene ring, and an electron-attractive functional group is allowed to bind to the other end thereof.
However, in the ground state, a molecule having the aforementioned structure has electric dipoles which tend to oppose each other to assume an energetically stable condition. Accordingly, when crystallized, the aforementioned molecule comes to have a structure with a symmetrical center. Because of the symmetrical structure, the large nonlinearity of each molecule can be canceled out at an entire crystal level. This feature of the crystallized structure has posed a problem that the excellent nonlinear optical effect expected on the basis of its molecular structure cannot be obtained at the entire crystal level.
For the reasons mentioned above, there has been a considerable demand for an organic nonlinear optical material having excellent nonlinearity not only at a molecular level, but also at the entire crystal level.
On the other hand, in the field of organic coloring agents, a wide variety of organic chelating agents have been used heretofore. In this field, Nilson reported oxalic bis(cyclohexylidene hydrazide) whose conventional name is cuprizone in 1950 [G. Nilson, Acta Chemica Scandinavia, 4,205 (1950)]. Since then, hydrazone compounds have been drawn attention as organic coloring agents for various metal ions. Characteristics which are required for the organic coloring agents include specificity, selectivity, sensitivity and the like. Since cuprizone is well-balanced in terms of such characteristics, it is widely used at present as a coloring agent for various metal ions. However, since the requirement for micro chemical analysis has increased over time, particularly, in absorption spectrophotometry, the development of an organic coloring agent more sensitive than the existing one is greatly demanded.